Implant system

ABSTRACT

The invention relates to an implant system containing at least one drill ( 5, 15 ) and one implant ( 32 ), particularly a dental implant, which can be screwed into a bore hole made in a bone ( 2 ) by means of a drill ( 6, 16 ). Preferably, the implant ( 32 ) comprises a self-cutting screw ( 34 ) with a thread core. The aim of the invention is to further develop an implant system which guarantees high primary stability for a wide variety of bone qualities and requires little technical complexity. According to the invention, the implant ( 32 ) and the drill ( 5, 15 ) are co-ordinated in such a manner according to bone quality that a compressed zone ( 28, 30 ) arises when the implant is screwed into the implant ( 32 ) in the bone ( 2 ). The size of said compressed zone is greater for low bone quality than for high bone quality.

[0001] The invention relates to an implant system, as defined by the distinguishing features given in the introductory portion of claim 1

[0002] An implant of this type is known, for example, from the U.S. Pat. No. 5,000,686. It is a dental implant with a self-cutting external thread. For inserting the implant, a borehole, the diameter of which corresponds essentially to the core diameter of the implant, is introduced into the jawbone by means of a drill. Subsequently, the implant is screwed into said borehole in the bone. In the case of the previously known implant, the core diameter of the thread, starting out from a cervical region, tapers towards an apical region, the depth of the thread being less in the cervical region than in the apical region. By these means, it is taken into account that the density of the bone is greater in the region of its upper edge than in lower lying areas. Classifications have therefore been proposed for different bone densities (qualities), for example, a classification of the alveolar bone into classes DI to DIV. The bone quality DI stands for a very cortical hard bone, while the bone quality DIV stands for a very spongy bone with very thin surrounding cortical substance. Such classifications of the bone quality take into consideration the strength, the size of pores, the compactness, the homogeneity, the density and the like of the bone.

[0003] Starting out from this, it is an object of the invention to propose an implant system, particularly with a dental implant, which enables the maximum, primary stability of the implant to be achieved in spite of the different starting conditions in the bony stratum. The implant system is to make it possible to insert the implant in a simple manner and to ensure the highest primary stability in all bone qualities. An instrumentarium and an implant are to be proposed, in order to be able to screw the implant functionally reliably into different bone qualities and to attain the highest possible primary stability.

[0004] This objective is accomplished in accordance with the distinguishing features of claim 1.

[0005] The inventive implant system enables the bony stratum to be prepared without problems by means of the drill or drills and the appropriately coordinated implant to be prepared as a function of the bone quality. The implant and in the drill or drills for preparing the bone stratum and for introducing the borehole are matched to one another in such a way, that an “internal condensation effect” is achieved as the implant is screwed in, particularly in the cervical bone region. The axial and/or radial dimensions of the zone in the bone, which is to be consolidated during the screwing in of the implant, are larger for bones of lower quality. For bones of different quality, the drill geometry and/or the depth of insertion of the drill are adapted; however, the design of the implants is not changed. A special (crestal) drill is provided for hard bones in the marginal or cervical region. Advisably, the zone, which is to be consolidated, lies in the crestal or cervical bone region, in the region of the opening in the upper edge of the bone and, moreover, preferably at a specified distance from the latter. Pursuant to the invention, especially the diameters of the thread core and the drill, assigned to the cervical bone region, are matched to one another in such a manner, that, the softer the bone, the greater is the condensation specified for the bone.

[0006] For the bone with the greatest possible hardness, especially of bone quality DI, the matching preferably is such that there is no condensation. When the implant is screwed in, the bone is consolidated particularly in the sub-cervical region, a high primary stability and a high-grade anchoring of the implant being ensured even in the case of bones of quality DII, DIII or DIV. On the other hand, pursuant to the invention, the implant is not pressed too strongly cervically into the bone, so that absorption of the bone, which would result from this, is avoided. Since the internal condensation takes place sub-cortically in the spongy region while the implant is being screwed in, undesirable, disadvantageous excessive bone stresses, as caused, for example, by consolidating and by tapping with the appropriate, suitable hand instruments, is avoided. Comfort for the patient is improved decisively by this technique. The size of the zone, which is to be consolidated, is determined especially by specifying the axial depth of a bone region, which starts out from the upper edge of the bone. In addition or alternatively, the core diameter of the crestal or cervical thread region and the borehole diameter of the cervical bone region can be specified as a function of the bone quality by the cervical or secondary drill for specifying the size and/or the cross section of the zone in the bone, which is to be consolidated while the implant is being screwed in.

[0007] Advantageously, a pilot drill is provided for introducing an initial pilot borehole in the bone, especially the jawbone, the depth of the pilot borehole being specified essentially by the length of the implant. In addition, the position and direction of the implant is fixed. Especially after the pilot borehole or preliminary borehole is introduced, a primary borehole is introduced pursuant to the invention by means of a primary drill, the diameter of the preliminary borehole being less than that of the primary borehole. The diameter of the primary drill and, accordingly, of the primary borehole corresponds at least approximately to the core diameter in the apical region of the implant. The apical end region of the primary borehole is also referred to below as the first borehole region. Within the scope of the invention and, for example, in the case of a conically tapering thread core in the cervical region of the implant, the primary borehole and/or the drill, intended for this borehole, can also be constructed correspondingly tapered at least for this region. Preferably, the bone quality is determined while drilling the pilot borehole and/or by means of drilled-out bone material. Furthermore, the bone quality can be determined by suitable diagnostic measures already before the preliminary borehole or primary borehole is introduced, for example, by x-rays or nuclear spin tomography. Subsequently, a secondary borehole, the depth of which advantageously corresponds to the bone quality, is introduced by means of the drill, which is constructed pursuant to the invention and referred to in the following also as cervical or secondary drill. In the case of a dense, compact bone, for example, of bone quality DI, a comparatively large depth is specified, which corresponds at least approximately to the length of the cervical region of the implant. The depth of the secondary borehole for a very cortical, hard bone advantageously is specified to be approximately half the size of the total length of the implant and/or at least approximately equal to the depth of the apical region. Preferably, the secondary drill has means for specifying the depth, to which it is introduced. These means are formed especially as markings at the outer surface or as stops or stop elements, which, if necessary, are mounted on the secondary drill. These means are constructed especially so that the drilling is stopped as soon as these means reach the upper edge of the bone.

[0008] The diameter of the secondary drill and/or of the secondary borehole advantageously is specified so that the implant can be lowered and/or screwed in without problems even into the dense, compact bone with out overloading the bone. For bones of low bone quality, the secondary borehole has a lesser depth. In the limiting case involving a soft bone, especially a bone corresponding to quality DIV, the depth of the secondary borehole is only such, that essentially only the cortical substance at the edge is removed. The condensation zone therefore commences at a distance from the upper edge of the bone, which is specified pursuant to the invention. Pursuant to the invention, the depth of the secondary borehole varies with the hardness of the bone, that is, the “harder” the bone, the deeper the borehole. Subsequently, the implant is screwed in to the borehole, which has been prepared pursuant to the invention, the apical region of the thread of the implant engaging the apical region of the primary borehole in a self-cutting manner. Since the diameter of the secondary borehole is at least approximately equal to the core diameter of the cervical region of the implant, the implant can be screwed without problems into a hard bone. In the case of soft bones, the screwing of the thread core, which is widened in comparison to the borehole or the drill in the cervical region of the implant, into the zone of the cervical bone region, which has not been drilled out, brings about an internal condensation effect, so that the bone in said zone of the cervical region is consolidated and, pursuant to the invention, the primary stability for high-grade anchoring of the implant is achieved also in soft bones.

[0009] Advantageously, only two drills are therefore required for the set of instruments for introducing the primary borehole and the secondary borehole in accordance with the bone quality. The drill for the second borehole advantageously has means, especially markings, which correspond to the depth, which is to be introduced. It should be noted here that implants with different diameters and/or different lengths usually are available. Consequently, the set of instruments contains drills matching the diameters of the implants and, moreover, in each case a drill for the primary borehole and a drill for the secondary borehole of the respective implant size and, optionally, also a preliminary drill. For implants of the same diameter but of different length, the same set of instruments are used, the primary drill and the appropriately provided preliminary drill having suitable means, such as markings or stop elements, for specifying the depth of the borehole, which corresponds to the length of the implant. Pursuant to the invention, the apical region of the thread, especially of the primary drill for implants of the same diameter and different length, is formed identically, the apical regions of the thread of the implants also being formed identically.

[0010] In accordance with the comments above, the implant contains a continuous thread, the core diameter of which is larger in the cervical region than in the apical region. The depth of the thread in the cervical region is, in particular, of the order of {fraction (1/10)} to {fraction (4/10)} mm and, in the apical region, advantageously between {fraction (4/10)} to {fraction (7/10)} mm. The thread core diameter in the apical region of the implant preferably is smaller by a specified amount than the thread core diameter in the cervical region and, in particular, corresponds essentially to the diameter of the primary drill in the second or apical region of the drill. The lengths of said thread regions are specified to be at least approximately identical and, moreover, preferably for all implants of the same diameter but of different lengths. For longer implants, an intermediate region is provided pursuant to the invention, the thread of which is essentially identical with that of the apical region and/or the thread core of which has a diameter, which is smaller than that in the cervical region by a specified amount.

[0011] Furthermore, within the scope of the invention, the implant can also be formed as a stepped screw, which has at least two thread regions or steps with different external diameters, the step at the apical end of the implant having the smallest external diameter. Such step implants are known, for example, from the EP patent 0 438 048. It is also of decisive importance for such embodiments that, especially by matching the diameter or diameters in the cervical region of the implant and the diameter or diameters of the boreholes in the cervical bone region and/or the depths of such regions as a function of the bone quality, an internal condensation or consolidation of the bone in a zone of specifiable magnitude is achieved preferably in the sub-cervical region, when the implant is screwed in.

[0012] Moreover, within the scope of the invention, other drill sets can also be provided as an alternative to the drill for the initial primary borehole and the drill for the secondary borehole. For example, several, especially four drills with thread steps of different lengths in the cervical region can be provided for implants of the same diameter for the secondary borehole, the lengths of the steps being matched to the quality of the bones and the diameters, adjoining the apical end, being matched to the diameter of the apical region of the thread of the implant. Moreover, the external diameters of the, for example, four drills in the cervical region can be specified differently depending on the different bone qualities. In this connection, the primary drilling can optionally also be carried out with a drill, the diameter of which is smaller than the core diameter of the apical region of the thread of the implant. Moreover, the use of a primary drill can optionally be omitted and the borehole can be introduced into the bone in a single step with a single drill of the set of four drills in accordance with the four bone qualities.

[0013] Further developments and special configurations of the invention are given in the dependent claims and in the following description of embodiments.

[0014] The invention is described in greater detail in the following by means of special examples, the invention not being limited to these examples. In the drawing

[0015]FIG. 1 shows a diagrammatic representation of the drill and of the boreholes introduced into the bone,

[0016]FIG. 2 shows a representation with a partially inserted implant,

[0017]FIG. 3 shows a representation with a completely inserted implant,

[0018]FIG. 4 shows the implant partly in a lateral view and partly in an axial section and

[0019] FIGS. 5 to 12 show sections through bone with four different bone qualities and the inserted implants.

[0020]FIG. 1 diagrammatically shows a section through a bone 2 with an upper edge 4, in which a primary borehole 6 or a first drilling region, indicated by broken lines, is introduced by means of a primary drill 5. The primary drill 5, which is also shown by broken lines, contains a shaft, which can be inserted in a known manner in a drilling device. The primary borehole 6 or the first drilling region has a diameter 8 and a length 9, which is at least equal to the length of the implant, which is not shown here. Outside of the bone 2 or above the upper edge 4, the drill 5 has a stop or a radial expansion 10 and at least one marking 11, which form means for specifying the depth, to which the primary borehole 6 is introduced. Furthermore, especially below the expansion 5, stop means can be provided for specifying or limiting the depth of introduction. Accordingly, boreholes, which are longer or deeper than the length 9 shown, can also be introduced with the same primary drill 5. The primary drill 5 or the primary drilling 6 contains an apical region 13, which is constructed to correspond to the apical region of the implant. The apical end region 13 is constructed identically for all implant length, whereas the axial length of an intermediate region 13 of the primary borehole 6 is specified in accordance to the length of the implant. For implants of the same diameter but different length 9, which preferably is specified in the region to be between 8 and 20 mm, the same primary drill 5 is used accordingly, the depth of introduction in the bone 2, however, being specified. The intermediate region 13, which, in particular, is cylindrical, advisably has the same diameter 8 as the cervical region, which adjoins in the direction of the upper edge 4 of the bone. Particularly in the apical end region 13, the drill 5 may also have a slightly conical external contour to correspond to that of the implant. This is indicated by the broken line 13′. Previously, a preliminary borehole can be introduced in the bone 2 by means of a preliminary drill as indicated by the line 12 of dots and dashes. The diameter 8 of the primary drill 5 or the primary borehole 6 corresponds essentially that of the thread core in the apical region of the implant, which is not shown here.

[0021] After the introduction of the primary borehole 6, a secondary borehole 16, with the crestal cervical diameter 17, was introduced by means of a secondary drill 15. Pursuant to the invention, the depth of the secondary borehole 16 and/or of a corresponding borehole region of the total borehole is specified to correspond to the different bone qualities, for example, DI to DIV. For the bone quality DI, that is, for a dense compact bone, the greatest depth is 18, for the bone quality DII the depth is 19, for the bone quality DIII the depth is 20 and for the bone quality DIV, that is for a very spongy bone with a very thin surrounding cortical substance, the depth is 21. The drill or secondary drill 15, shown by means of lines and dots and dashes, preferably has means for the depth of introduction, these means preferably being formed by markings 22, which are disposed at the outer surface of the drill 15. These marking 22 are spaced apart from one another to correspond to the depths of introduction 18 to 21.

[0022] The lower edge of a cervical thread region of an implant, inserted in the direction of the longitudinal axis 24 into the borehole of the bone, so prepared, is indicated by the means of a line 23. The cervical region of the thread has a core diameter 26, which is, at least approximately, equal in size to that of the exterior diameter of the secondary drill 15 or to the internal diameter 17 of the secondary borehole 16. After the implant is inserted, the lower edge of the implant, corresponding to the line 23 of the cervical thread region, is separated from the upper edge 4 of the bone by a distance, which is essentially equal in size to the depth 18 for the best bone quality DI. Accordingly, for this bone quality, the implant can be screwed in a known manner and/or with the usually permissible expenditure of force into the bone 2, the thread flanks of the cervical thread region cutting into the surrounding cervical bone region over the region of the secondary borehole extending to the depth 18. In the event of a lesser bone quality DII, the secondary borehole is introduced only to the depth 19, so that the primary borehole 6 with the diameter 8 adjoins apically thereon. Accordingly, a zone 28 is present in the cervical bone region between the lower edge of the primary borehole of depth 19 and the line 22. As the implant is being screwed in, the bone material in this zone 28 is displaced laterally and consolidated by the cervical thread core. Analogously, zones of the bone, which are to be consolidated as the implant is screwed in, are created corresponding to the depths 20, 21 for bones of qualities DIII and DIV. For a relatively soft bone or for the lowest bone quality DIV, the primary borehole is expanded corresponding to the depth 21 by means of the secondary drill 15 to the diameter 17 only in the region adjoining the upper edge 4 of the bone. In the region with the depth 21, adjoining the upper edge 4 of the bone, there is therefore no condensation and any undesirable tearing out of the bone is thus avoided reliably. In this region, a preferably thread-free neck region is in contact with the bone.

[0023]FIG. 2 shows the borehole so prepared and having an opening 3 8 at the upper edge 4, with a partially inserted implant 32, which is constructed as a screw implant with a self-cutting, continuous outer thread 34 with an external diameter 35 of the tip of the thread. In the cervical region 36, which, according to the drawing, is above the upper edge 4, the thread 34 of the implant 32 has a core diameter 26, which is larger, by a specified amount, than the core diameter 40 in the apical region 42. The core diameter 40 is at least approximately as large as the diameter 8 of the primary borehole 6. The lower edge of the cervical region 36 lies here level with the upper edge 4 of the bone. As can be seen, the implant in the apical region 42 is formed so as to taper conically towards the apical end. Adjoining the cervical region 36 in the direction of the apical end, a transition region 43 is provided, in which the core diameter 26 changes over at least approximately continuously into the core diameter 40. This transition region 43 extends preferably over at least 360° or over one thread and especially over approximately 7200 or two threads. In particular, at most three threads are present. The length of the transition region 43 is significantly less than that of the cervical region 36 and/or of the apical region 42. Accordingly, as the implant is screwed into the borehole prepared in accordance with the above comments, the bone is displaced gently and radially into the tissue and consolidated by means of the transition region 43. As can be seen, the implant has cutting grooves 44 in the apical region 42, advisedly such cutting grooves being distributed over the periphery. Pursuant to the invention, the core diameter 26 of the implant thread in the cervical region 36 is larger by a specified amount than the diameter 8 of the primary borehole or of the drill, with which the latter was introduced into the cervical bone region. Accordingly, as the implant 32 is screwed further into the bone, condensation of the bone in the zones explained above by means of FIG. 1 takes place in the sub-cervical region of the bone because of this diameter difference.

[0024] Alternatively, within the scope of the invention, the cervical bone region can be prepared by means of the drill in such a manner that, instead of the different depths in the cervical region, different diameters of the primary borehole are introduced into the bone by means of appropriately constructed drills. A lesser diameter is specified for a soft bone, for example, of quality DIV, than for a harder bone, for example, of quality DII. Preferably, a diameter difference between the thread core and the borehole diameter of at least 0.05 mm is specified in the case of a quite hard cortical bone, for example, of the bone quality DI.

[0025]FIG. 3 shows the implant 32, which is inserted completely in the bone 2 and the preferably thread-free neck region 45 of which passes through the upper edge 4 of the bone. The neck region 45 is in contact with the cortical material, as a result of which a stable anchoring of the implant in the cortical material is achieved in an advantageous manner. For the bone quality DI, in accordance with the depth 18 of the secondary borehole, a ring-shaped bone core is removed completely in such a manner, that the implant is lowered and screwed essentially freely and without problems into the bone, the thread being screwed into the bone in a known manner. For softer bone qualities, corresponding to depths 19, 20 and 21, the bone assigned to the cervical region 36 of the implant 32 is displaced laterally and condensed in the zones described above, as indicated by arrows 48, 49.

[0026]FIG. 4 shows the implant 32 partially in a side view and partially in a sectional view. The implant preferably is a dental implant and/or constructed as a titanium screw implant and contains an inner borehole 50 with an internal thread 52 for the holding screw, by means of which a setting-upper part can be connected with the implant 32 in a known manner. The borehole 50 furthermore contains seating means 54, especially in the form of a hexagon socket, for a tool, by means of which the implant 32 can be screwed into the bone. Furthermore, the borehole 50, adjoining the plateau 46, contains a centering surface 56, especially a cylindrical centering surface 56, for the setting-up element. As can be seen, the depth 58 of the thread in the cervical region 36 increases towards the apical region 42. In the apical region 42, the implant has a thread depth 60.

[0027] In a particular development, the lead at the upper side 62 of the thread flanks is less by a specified factor than the lead at the underside 64. Accordingly, the lead at the upper side 62, particularly of the order of {fraction (1/10)}, is less than that at the underside 64. Accordingly, with increasing height, the profile at the thread flank becomes narrower with the result that, as the implant is screwed in, the increase in friction in the bone becomes less. By these means, it is avoided that the friction between the implant and the bone in “a hard bone” increases with increasing implant length. Accordingly, the lead at the upper side 62 is specified, especially, to be of the order of 0.86 and, at the underside 64, to be of the order of 0.87.

[0028] Example of an Instrument Set and of an Implant Diameter of the preliminary drill 2.0 mm Diameter of the primary drill 3.5 mm Diameter of the secondary drill 3.9 mm Cervical core diameter 26 of the implant 3.8 mm Apical core diameter 40 of the implant 3.4 mm Crestal thread depth 58 0.2 mm Apical thread depths 60 0.5 mm

[0029]FIG. 5 diagrammatically shows a section through a dense, compact bone corresponding to bone quality DI. The borehole, introduced into this bone, has the comparatively large depth 18 in the region adjoining the upper edge 4. According to FIG. 6, the implant 32 is screwed into the borehole, so produced. As can be seen, the cervical region of the implant 32 essentially is as long as the depth 18, so that the implant 32 can be screwed without problems and/or freely into the dense and compacted bone.

[0030]FIG. 7 diagrammatically shows a porous, compact bone of quality DII. In comparison to FIG. 5, the depth 19 for the secondary borehole is less. According to FIG. 8, the implant 32 is screwed once again into the borehole so prepared. Since the length of the cervical region of the implant 32 is greater that the depth 19 of the assigned borehole part, the bone in zone 28 in the cervical region is consolidated correspondingly, so that, in spite of a reduced bone quality, a high primary stability is assured.

[0031]FIG. 9 shows a section through a relative porous spongy bone with comparatively thin, surrounding cortical material corresponding to bone quality DIII. The depth 20 of the secondary borehole in this bone is even less. Consequently, as shown in FIG. 10, the zone 29 of the bone, which is enlarged in comparison to FIG. 8, is consolidated by means of the cervical region 36 of the implant 32.

[0032] Finally, FIG. 11 shows a very spongy bone of quality DIV, which is surrounded by very thin cortical material. An extremely slight depth 21 is specified for the secondary borehole. Accordingly, as shown in FIG. 12, the bone in zone 30 is consolidated practically over the whole length of the cervical region 36 of the implant 32, so that the required primary stability for a high grade anchoring of the implant is assured.

[0033] It should be noted explicitly here that, in the implant system, the same implants 32 with the same diameter are always used, independently of the bone quality, the high primary stability being assured by a depth of the secondary borehole, specified for the bone quality, and/or by the size of the zones assigned especially to cervical implant region, which are matched to the particular bone quality. Moreover, the same drill is always used for implants 32 of the same diameter but of a different length. It is self-evident that the implant system for implants of other diameters furthermore has drills with appropriately matched diameters. For example a complete implant system for implants with different diameters of, for example, 3 mm, 3.4 mm, 3.8 mm, 4.5 mm, 5.5 mm comprises in each case, an assigned set of drills, particularly preliminary drills, primary drills and secondary drills, by means by which the boreholes are produced in the bones for implants of the respective diameters but of different lengths in accordance with the comments above.

List of Reference Numbers

[0034]2 Bone

[0035]4 Upper edge of 2

[0036]5 Primary drill

[0037]6 Primary borehole/drilling region

[0038]7 Shaft of 5

[0039]8 Diameter of 5 or 6

[0040]9 Length of 5 or 6

[0041]10 Stop/expansion of 5

[0042]11 Marking

[0043]12 Line of dots and dashes/preliminary borehole

[0044]13 Apical end region

[0045]14 Intermediate region of 6

[0046]15 Secondary drill

[0047]16 Secondary borehole/second drilling region

[0048]17 Crestal diameter of 16

[0049]18-21 Depths of 16

[0050]22 Means/marking

[0051]23 Line

[0052]24 Longitudinal axis

[0053]26 Core diameter of implant thread in 36

[0054]28, 29, 30 Zone which is to be consolidated

[0055]32 Implant

[0056]34 Thread of 32

[0057]35 External diameter of 34

[0058]36 Cervical region of 32

[0059]38 Opening

[0060]40 Core diameter in 42

[0061]42 Apical region of 32

[0062]43 Transition region from 26 to 40

[0063]44 Cutting groove

[0064]45 Neck region

[0065]46 Plateau

[0066]48, 49 Arrow

[0067]50 Inner borehole

[0068]52 Internal thread

[0069]54 Seating means

[0070]56 Centering surface

[0071]58 Thread depth in 36

[0072]60 Threat depth in 42

[0073]62 Upper side of 34

[0074]64 Underside of 34 

1. An implant system, containing at least one drill (5, 15) and an implant (32), especially a dental implant, which can be screwed into a borehole (6, 16), produced by means of a drill in a bone (2), the implant (32) preferably having a self-cutting thread (34) with a thread core, characterized in that the implant (32) and the drill (5, 15) are matched to one another as a function of the bone quality in such a manner that, after the implant (32) is screwed into the bone (2), a consolidated zone (28 to 30) is present, the size of which is less when the bone quality is low than when the bone quality is higher.
 2. The implant system of claim 1, characterized in that the consolidated zone (28 to 30) is assigned to a sub-cervical region of the implant (32) and/or in that the consolidated zone (28 to 30) commences at a depth (21) from a specified distance from an upper edge (4) of the bone (2).
 3. The implant system of claims 1 or 2, characterized in that the diameter (26) of the thread core of the implant (32) in the zone (28 to 30) and/or in the cervical region (36) is greater than the diameter of the drill, the diameter of the thread core being different from that of the drill.
 4. The implant system especially of one of the claims 1 to 3, characterized in that the length and/or the size of the zone (28 to 30) is specified as function of the density of the bone (2) in such a manner, that for a bone of low density, the length and/or the diameter difference of the zone (30) is greater than the length (28) and/or the diameter difference for a bone of high density.
 5. The implant system of one of the claims 1 to 4, characterized in that the implant (32), in the direction of the apical end adjoining the cervical region (36), has a transition region (43), in which the core diameter (26) changes over preferably continuously into an apical region (42) of the thread with a reducing core diameter (40) and/or that the transition region (43) extends at least about one peripheral angle of 360° and preferably a peripheral angle of 720° and/or not more than three threads.
 6. The implant system, especially of one of the claims 1 to 5, characterized in that a primary drill (5) is provided, which has a diameter (8) at least in the cervical region, and that a secondary drill (15) is provided, the diameter (17) of which is larger by a specified amount than said diameter (8) of the primary drill (5), and/or that the core diameter of the implant (32) in the cervical region (36) is essentially as large as the diameter (17) of the secondary drill (15) and/or that the external diameter (35) of the crest of the teeth of the thread (34) of the implant (32) in the cervical region (36) is greater than said diameter (17) of the secondary drill (15).
 7. The implant system of one of the claims 1 to 6, characterized in that the secondary drill (15) has means (22), especially markings, for specifying, in accordance with the bone quality, the depth to which the implant is to be brought into the bone.
 8. The implant system of one of the claims 1 to 7, characterized in that the zone (28-30), which is to be consolidated, is assigned to a cervical region (36) of the implant (32) and/or is specified by means of a second borehole region (16), which commences especially at the spongiosa and/or is at a distance from the upper edge of the bone (2), and/or that the borehole (6, 16) is produced in the bone (2) as a function of the bone quality in such a manner, that the implant (32) can be screwed in essentially freely if the bone quality is good.
 9. The implant system of one of the claims 1 to 8, characterized in that the borehole (6, 16) is produced in such a manner, that the borehole region (16), assigned especially to a cervical region (26) of the implant (32), has a depth (18-21), which is deeper for bones of density than for bones of a lower density, and/or that the length (9) of the primary borehole (6) is at least as large as the length of the implant (32) and/or that the diameter (8) of the primary borehole is essentially as large as the core diameter (40) of an apical region (42) of the implant (32).
 10. The implant system of one of the claims 1 to 9, characterized in that the second borehole region (16), preferably assigned to the cervical region (36) of the implant (32), is produced by means of a secondary drilling process, preferably commencing at the upper edge (4) of the bone (2), and/or that the second borehole region (16) has a diameter (17), which is essentially as large as the core diameter (26) in the cervical region (36) of the implant region (32).
 11. The implant system of one of the claims 1 to 10, characterized in that the depth (18) of the secondary drilling process and/or of the secondary borehole region (16) is specified to be significantly greater for a comparatively stable bone than the depth (21) in an appreciably spongy bone and/or that the depth (18) of the second borehole region and/or of the secondary drilling process (16) is essentially only half as large in the case of a stable bone, especially bone of quality DI, as the total length (9) of the borehole and/or of the implant (32) and/or that, for a quite spongy bone, especially a bone of quality DIV, the depth (21) of the second bone region and/or of the secondary drilling process (16) is essentially the same size as the thickness of the cortical material surrounding the bone.
 12. The implant system of one of the claims 1 to 1, characterized in that the primary drill (5) for producing the primary borehole (6) and, furthermore, the secondary drill (15) for producing the secondary borehole (16) as well as an implant (32) are provided, it being possible to produce the primary borehole with a depth, corresponding to the length of the implant (36), by means of the primary drill (5), and that the secondary drill (16), for producing the secondary borehole (16) in the bone (2), can be introduced to different depths (18-21) from the upper edge (4) on the bone (2) depending on the bone quality.
 13. The implant system of one of the claims 1 to 12, characterized in that the secondary drill (15) has markings (22), which correspond to the different bone qualities, the introduction of the secondary borehole (16) being stopped especially when the upper edge (4) of the bone (2) reaches a marking assigned to the quality of the bone and the depth of the secondary borehole (16) matched to the bone quality, being specified in this way.
 14. The implant system of one of the claims 1 to 13, characterized in that identically constructed implants (32) are provided for the different bone qualities and/or in each case a primary drill (5) and a secondary drill (15) are provided for implants (32) of different size and/or different core diameter (36), a preliminary drill being preferably provided in each case, the diameter of which is smaller than the diameter of the respective primary drill (5). 